The unique electrical and optical properties and high surface activity feature of one-dimensional nanowires (tubes) materials have attracted great interest in recent years. There are many ways to fabricate Si nanowires (tubes) at present, including a laser ablation (Morales A M, Lieber C M. Science, 1998, 279(9):208˜211; Lee C S, Wang N, Tang Y H, et al. MRS. Bulletin., 1999:36˜41), a chemical vapor deposition (CVD) (Wang N L, Zhang Y J, Zhu J. Journal of Materials Science Letters, 2001, 20:89˜91), a plasma enhanced chemical vapor deposition (PECVD) (Zeng X B, Xu Y Y, Zhang S B, et al. Journal of Crystal Growth, 2003, 247 (1):13˜16), a thermal vapor deposition (Feng S Q, Yu D P, Zhang H Z, et al. Journal of Crystal Growth, 2000, 209:513˜517), a solution technique (Holmes J D, Johnston K P, Doty R C, et al. Science, 2000, 287:1471˜1473), a selective plating (Lew K K, Redwing J M. Journal of Crystal Growth, 2003, 254(1):14˜22) and a hydrothermal deposition (Pei L Z, Tang Y H, Chen Y W, et al. Journal of Crystal Growth, 2005, 289:423˜427). Nanowires produced by a laser ablation method have high yield and high purity. But its shortcoming is high costs for expensive equipments. On the contrary, chemical vapor deposition (CVD) and thermal chemical vapor deposition techniques are relatively low costs, but the products' diameters vary over a wide range. The products also contain plentiful nano-chains. Solution-grown technique can produce nanowires with high length-diameter ratio, but requires using noble metals as catalyst. In addition, the organic and toxic solution has to be recycled, since it will pollute the environment. Other techniques, such as selective plating etc., the yields of nanowires are quite low. The shortcomings of all the above-mentioned techniques hamper the industrial use of nanowires.
In molten salt studies, the electrochemical method of fabricating metal, alloy and non-metal directly from solid compounds by electrolysis has been provided by Fray Derek John, Farthing Thomas William and Chen Zheng of Cambridge GB, therefore this method is also called FFC Cambridge techniques. The FFC Cambridge method has advantages over other methods. It uses solid compounds to fabricate metal, alloy and non-metal by a one-step electrolysis, thereby it shortens the production process, saves energy and reduces pollution and costs. Since the composition and the reduction level of the materials can be controlled, this method is used in functional materials production. Both international publications “Removal of oxygen from metal oxides and solid solutions by Electrolysis in a fused salt” (WO1999/064638) and “Metal and alloy powders and powder fabrication” (WO2002/040725) by this Cambridge team claimed the technique for fabricating silicon powder directly from solid SiO2 powder. Japanese patent (JP2006/321688) also discloses a method for producing silicon powder by using silicon dioxide powder mixed with silicon or single crystal silicon wafer as conductor, and electrolyzing high-purity quartz. Micron silicon powder is produced by using the methods disclosed by above three patents. However, electrochemical methods for fabricating silicon nanopowder, silicon nanowires (tubes) from silicon compound SiX or silicon mixture comprising silicon compound SiX have not been published.